rtc: st: Add new driver for ST's LPC RTC

ST's Low Power Controller (LPC) controls two devices; watchdog and RTC.
Only one of the devices can be used at any one time.  This is enforced
by the correlating MFD driver.  This portion of the driver-set controls
the Real Time Clock.

Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

3 files changed, 366 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 6149ae01e11f..8b8b332efaed 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1510,6 +1510,17 @@ config RTC_DRV_SIRFSOC
           Say "yes" here to support the real time clock on SiRF SOC chips.
           This driver can also be built as a module called rtc-sirfsoc.
 
+config RTC_DRV_ST_LPC
+        tristate "STMicroelectronics LPC RTC"
+        depends on ARCH_STI
+        depends on OF
+        help
+          Say Y here to include STMicroelectronics Low Power Controller
+          (LPC) based RTC support.
+
+          To compile this driver as a module, choose M here: the
+          module will be called rtc-st-lpc.
+
 config RTC_DRV_MOXART
         tristate "MOXA ART RTC"
         depends on ARCH_MOXART || COMPILE_TEST
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index c31731c29762..411e630f36b9 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -153,4 +153,5 @@ obj-$(CONFIG_RTC_DRV_WM8350)	+= rtc-wm8350.o
 obj-$(CONFIG_RTC_DRV_X1205)     += rtc-x1205.o
 obj-$(CONFIG_RTC_DRV_XGENE)     += rtc-xgene.o
 obj-$(CONFIG_RTC_DRV_SIRFSOC)   += rtc-sirfsoc.o
+obj-$(CONFIG_RTC_DRV_ST_LPC)    += rtc-st-lpc.o
 obj-$(CONFIG_RTC_DRV_MOXART)    += rtc-moxart.o
diff --git a/drivers/rtc/rtc-st-lpc.c b/drivers/rtc/rtc-st-lpc.c
new file mode 100644
index 000000000000..3f9d0acb81c7
--- /dev/null
+++ b/drivers/rtc/rtc-st-lpc.c
@@ -0,0 +1,354 @@
+/*
+ * rtc-st-lpc.c - ST's LPC RTC, powered by the Low Power Timer
+ *
+ * Copyright (C) 2014 STMicroelectronics Limited
+ *
+ * Author: David Paris <david.paris@st.com> for STMicroelectronics
+ *         Lee Jones <lee.jones@linaro.org> for STMicroelectronics
+ *
+ * Based on the original driver written by Stuart Menefy.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+
+#include <dt-bindings/mfd/st-lpc.h>
+
+/* Low Power Timer */
+#define LPC_LPT_LSB_OFF         0x400
+#define LPC_LPT_MSB_OFF         0x404
+#define LPC_LPT_START_OFF       0x408
+
+/* Low Power Alarm */
+#define LPC_LPA_LSB_OFF         0x410
+#define LPC_LPA_MSB_OFF         0x414
+#define LPC_LPA_START_OFF       0x418
+
+/* LPC as WDT */
+#define LPC_WDT_OFF             0x510
+#define LPC_WDT_FLAG_OFF        0x514
+
+struct st_rtc {
+        struct rtc_device *rtc_dev;
+        struct rtc_wkalrm alarm;
+        struct resource *res;
+        struct clk *clk;
+        unsigned long clkrate;
+        void __iomem *ioaddr;
+        bool irq_enabled:1;
+        spinlock_t lock;
+        short irq;
+};
+
+static void st_rtc_set_hw_alarm(struct st_rtc *rtc,
+                                unsigned long msb, unsigned long  lsb)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&rtc->lock, flags);
+
+        writel_relaxed(1, rtc->ioaddr + LPC_WDT_OFF);
+
+        writel_relaxed(msb, rtc->ioaddr + LPC_LPA_MSB_OFF);
+        writel_relaxed(lsb, rtc->ioaddr + LPC_LPA_LSB_OFF);
+        writel_relaxed(1, rtc->ioaddr + LPC_LPA_START_OFF);
+
+        writel_relaxed(0, rtc->ioaddr + LPC_WDT_OFF);
+
+        spin_unlock_irqrestore(&rtc->lock, flags);
+}
+
+static irqreturn_t st_rtc_handler(int this_irq, void *data)
+{
+        struct st_rtc *rtc = (struct st_rtc *)data;
+
+        rtc_update_irq(rtc->rtc_dev, 1, RTC_AF);
+
+        return IRQ_HANDLED;
+}
+
+static int st_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+        struct st_rtc *rtc = dev_get_drvdata(dev);
+        unsigned long lpt_lsb, lpt_msb;
+        unsigned long long lpt;
+        unsigned long flags;
+
+        spin_lock_irqsave(&rtc->lock, flags);
+
+        do {
+                lpt_msb = readl_relaxed(rtc->ioaddr + LPC_LPT_MSB_OFF);
+                lpt_lsb = readl_relaxed(rtc->ioaddr + LPC_LPT_LSB_OFF);
+        } while (readl_relaxed(rtc->ioaddr + LPC_LPT_MSB_OFF) != lpt_msb);
+
+        spin_unlock_irqrestore(&rtc->lock, flags);
+
+        lpt = ((unsigned long long)lpt_msb << 32) | lpt_lsb;
+        do_div(lpt, rtc->clkrate);
+        rtc_time_to_tm(lpt, tm);
+
+        return 0;
+}
+
+static int st_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+        struct st_rtc *rtc = dev_get_drvdata(dev);
+        unsigned long long lpt;
+        unsigned long secs, flags;
+        int ret;
+
+        ret = rtc_tm_to_time(tm, &secs);
+        if (ret)
+                return ret;
+
+        lpt = (unsigned long long)secs * rtc->clkrate;
+
+        spin_lock_irqsave(&rtc->lock, flags);
+
+        writel_relaxed(lpt >> 32, rtc->ioaddr + LPC_LPT_MSB_OFF);
+        writel_relaxed(lpt, rtc->ioaddr + LPC_LPT_LSB_OFF);
+        writel_relaxed(1, rtc->ioaddr + LPC_LPT_START_OFF);
+
+        spin_unlock_irqrestore(&rtc->lock, flags);
+
+        return 0;
+}
+
+static int st_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
+{
+        struct st_rtc *rtc = dev_get_drvdata(dev);
+        unsigned long flags;
+
+        spin_lock_irqsave(&rtc->lock, flags);
+
+        memcpy(wkalrm, &rtc->alarm, sizeof(struct rtc_wkalrm));
+
+        spin_unlock_irqrestore(&rtc->lock, flags);
+
+        return 0;
+}
+
+static int st_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+        struct st_rtc *rtc = dev_get_drvdata(dev);
+
+        if (enabled && !rtc->irq_enabled) {
+                enable_irq(rtc->irq);
+                rtc->irq_enabled = true;
+        } else if (!enabled && rtc->irq_enabled) {
+                disable_irq(rtc->irq);
+                rtc->irq_enabled = false;
+        }
+
+        return 0;
+}
+
+static int st_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+        struct st_rtc *rtc = dev_get_drvdata(dev);
+        struct rtc_time now;
+        unsigned long now_secs;
+        unsigned long alarm_secs;
+        unsigned long long lpa;
+
+        st_rtc_read_time(dev, &now);
+        rtc_tm_to_time(&now, &now_secs);
+        rtc_tm_to_time(&t->time, &alarm_secs);
+
+        /* Invalid alarm time */
+        if (now_secs > alarm_secs)
+                return -EINVAL;
+
+        memcpy(&rtc->alarm, t, sizeof(struct rtc_wkalrm));
+
+        /* Now many secs to fire */
+        alarm_secs -= now_secs;
+        lpa = (unsigned long long)alarm_secs * rtc->clkrate;
+
+        st_rtc_set_hw_alarm(rtc, lpa >> 32, lpa);
+        st_rtc_alarm_irq_enable(dev, t->enabled);
+
+        return 0;
+}
+
+static struct rtc_class_ops st_rtc_ops = {
+        .read_time              = st_rtc_read_time,
+        .set_time               = st_rtc_set_time,
+        .read_alarm             = st_rtc_read_alarm,
+        .set_alarm              = st_rtc_set_alarm,
+        .alarm_irq_enable       = st_rtc_alarm_irq_enable,
+};
+
+static int st_rtc_probe(struct platform_device *pdev)
+{
+        struct device_node *np = pdev->dev.of_node;
+        struct st_rtc *rtc;
+        struct resource *res;
+        struct rtc_time tm_check;
+        uint32_t mode;
+        int ret = 0;
+
+        ret = of_property_read_u32(np, "st,lpc-mode", &mode);
+        if (ret) {
+                dev_err(&pdev->dev, "An LPC mode must be provided\n");
+                return -EINVAL;
+        }
+
+        /* LPC can either run in RTC or WDT mode */
+        if (mode != ST_LPC_MODE_RTC)
+                return -ENODEV;
+
+        rtc = devm_kzalloc(&pdev->dev, sizeof(struct st_rtc), GFP_KERNEL);
+        if (!rtc)
+                return -ENOMEM;
+
+        spin_lock_init(&rtc->lock);
+
+        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        rtc->ioaddr = devm_ioremap_resource(&pdev->dev, res);
+        if (IS_ERR(rtc->ioaddr))
+                return PTR_ERR(rtc->ioaddr);
+
+        rtc->irq = irq_of_parse_and_map(np, 0);
+        if (!rtc->irq) {
+                dev_err(&pdev->dev, "IRQ missing or invalid\n");
+                return -EINVAL;
+        }
+
+        ret = devm_request_irq(&pdev->dev, rtc->irq, st_rtc_handler, 0,
+                               pdev->name, rtc);
+        if (ret) {
+                dev_err(&pdev->dev, "Failed to request irq %i\n", rtc->irq);
+                return ret;
+        }
+
+        enable_irq_wake(rtc->irq);
+        disable_irq(rtc->irq);
+
+        rtc->clk = clk_get(&pdev->dev, NULL);
+        if (IS_ERR(rtc->clk)) {
+                dev_err(&pdev->dev, "Unable to request clock\n");
+                return PTR_ERR(rtc->clk);
+        }
+
+        clk_prepare_enable(rtc->clk);
+
+        rtc->clkrate = clk_get_rate(rtc->clk);
+        if (!rtc->clkrate) {
+                dev_err(&pdev->dev, "Unable to fetch clock rate\n");
+                return -EINVAL;
+        }
+
+        device_set_wakeup_capable(&pdev->dev, 1);
+
+        platform_set_drvdata(pdev, rtc);
+
+        /*
+         * The RTC-LPC is able to manage date.year > 2038
+         * but currently the kernel can not manage this date!
+         * If the RTC-LPC has a date.year > 2038 then
+         * it's set to the epoch "Jan 1st 2000"
+         */
+        st_rtc_read_time(&pdev->dev, &tm_check);
+
+        if (tm_check.tm_year >=  (2038 - 1900)) {
+                memset(&tm_check, 0, sizeof(tm_check));
+                tm_check.tm_year = 100;
+                tm_check.tm_mday = 1;
+                st_rtc_set_time(&pdev->dev, &tm_check);
+        }
+
+        rtc->rtc_dev = rtc_device_register("st-lpc-rtc", &pdev->dev,
+                                           &st_rtc_ops, THIS_MODULE);
+        if (IS_ERR(rtc->rtc_dev)) {
+                clk_disable_unprepare(rtc->clk);
+                return PTR_ERR(rtc->rtc_dev);
+        }
+
+        return 0;
+}
+
+static int st_rtc_remove(struct platform_device *pdev)
+{
+        struct st_rtc *rtc = platform_get_drvdata(pdev);
+
+        if (likely(rtc->rtc_dev))
+                rtc_device_unregister(rtc->rtc_dev);
+
+        return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int st_rtc_suspend(struct device *dev)
+{
+        struct st_rtc *rtc = dev_get_drvdata(dev);
+
+        if (device_may_wakeup(dev))
+                return 0;
+
+        writel_relaxed(1, rtc->ioaddr + LPC_WDT_OFF);
+        writel_relaxed(0, rtc->ioaddr + LPC_LPA_START_OFF);
+        writel_relaxed(0, rtc->ioaddr + LPC_WDT_OFF);
+
+        return 0;
+}
+
+static int st_rtc_resume(struct device *dev)
+{
+        struct st_rtc *rtc = dev_get_drvdata(dev);
+
+        rtc_alarm_irq_enable(rtc->rtc_dev, 0);
+
+        /*
+         * clean 'rtc->alarm' to allow a new
+         * .set_alarm to the upper RTC layer
+         */
+        memset(&rtc->alarm, 0, sizeof(struct rtc_wkalrm));
+
+        writel_relaxed(0, rtc->ioaddr + LPC_LPA_MSB_OFF);
+        writel_relaxed(0, rtc->ioaddr + LPC_LPA_LSB_OFF);
+        writel_relaxed(1, rtc->ioaddr + LPC_WDT_OFF);
+        writel_relaxed(1, rtc->ioaddr + LPC_LPA_START_OFF);
+        writel_relaxed(0, rtc->ioaddr + LPC_WDT_OFF);
+
+        return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(st_rtc_pm_ops, st_rtc_suspend, st_rtc_resume);
+
+static const struct of_device_id st_rtc_match[] = {
+        { .compatible = "st,stih407-lpc" },
+        {}
+};
+MODULE_DEVICE_TABLE(of, st_rtc_match);
+
+static struct platform_driver st_rtc_platform_driver = {
+        .driver = {
+                .name = "st-lpc-rtc",
+                .pm = &st_rtc_pm_ops,
+                .of_match_table = st_rtc_match,
+        },
+        .probe = st_rtc_probe,
+        .remove = st_rtc_remove,
+};
+
+module_platform_driver(st_rtc_platform_driver);
+
+MODULE_DESCRIPTION("STMicroelectronics LPC RTC driver");
+MODULE_AUTHOR("David Paris <david.paris@st.com>");
+MODULE_LICENSE("GPL");